Answer Posted / amit rajoria

Yes, we can use multiple Null values in case of Unique Key
Column. This is one the main difference between Unique Key
and Primary Key that Unique Key always allows multiple
entries of Null Statement where as Primary Key never allows
this.

I am hereby giving you a very very basic example which
suggests that Unique Key can have more than one Null
Statement :-

SQL> create table abcd(name varchar2(10) unique);

Table created.

**********************

Now insert the values :-

SQL> insert into abcd(name)values('amit');

1 row created.

SQL> insert into abcd(name)values('ami');

1 row created.

SQL> insert into abcd(name)values(null);

1 row created.

SQL> insert into abcd(name)values(null);

1 row created.

SQL> insert into abcd(name)values(null);

1 row created.

SQL> commit;

Commit complete.

SQL> select * from abcd;

NAME
----------
amit
ami



Here blank space above represents the entries of null
statements..!!

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